1. Field of the Invention
The invention relates to an automatic system of manufacturing ball studs for vehicles, in particular to an automatic system which can diagnose each process and perform production and inventory control through establishing various processes inline to automatically manufacture ball studs for vehicles.
2. Description of the Related Art
In general, a ball stud is cold forged or machine worked after a steel rod is cut into pieces of a desired size for ball studs as shown in FIG. 1. Here, the cold forged piece is formed of a head, threads, a tapered part and a neck for a ball stud. The cold forged steel piece is strengthened through heat treatment, quenching, and annealing or tempering. The threads of the cold forged piece is formed of a pin hole through a pin hole machining to prevent unscrewing and separating of a nut. Then, the process is carried out in the sequence of machine-cutting the head, burnishing the tapered part, the neck and the head, and thread-rolling the threads.
Techniques of the prior art, even though automated, can not depart from a lot production method and thus productivity enhancement can not be expected. Namely, spheroidized material of cold forging is put into a barret, cleaned, and heat treated through annealing, tempering and etc. A pin hole is machined, and then a head and a neck are machined to form a shape similar to a finished article. After machining, the head is burnished to obtain a desired surface illuminance. Then, a nut which is subjected to the final fabrication is machined. The machining method undergoes rolling process.
The cold forged piece in (a) of FIG. 1 is automatically produced by using a part former. The produced piece is cleaned to eliminate minute burrs and surface treated parts. In (b) and (c) of FIG. 1, heat treatment is performed to enhance strength and toughness of the structural steel material. Here, the heat treatment satisfies strength, hardness and toughness regulated in KS, i.e., Korean (Industrial) Standards. A pin hole is machined in (d) of FIG. 1. In (e) of FIG. 1, the piece is cut by using NC machine to obtain substantially same size as the finished article. (f) of FIG. 1 shows burnishing, in which ball joint should satisfy high illuminance regulation since it is a key part of carrying out continuous relative motion. Then, rolling of the threads is performed to finish the process for manufacturing a ball stud.
The process like this, however, has a lot production method which obstructs productivity enhancement, and as an article is machined, additional production cost is required for material, fabrication and other processes, and it is difficult to reduce production period. Also, as the cold forged article is cut, strength of the article degrades and thus property of the article may deteriorate.
In particular, various proposals about the head and neck rolling of ball studs for ball joints have been presented, one of which is disclosed in Japanese Open Patent Application Publication No. Sho 61-38730. In this document, a jig is correspondingly machined toward a neck, and a head is machined in various processes to realize a desired illuminance, so that production period is increased to degrade productivity. Also, cold forging is accompanied by cutting and thus excellent article properties may not be obtained.
The invention is proposed to solve the foregoing problems, which has an object to provide an automatic system of manufacturing ball studs for vehicles in which various processes from cold forging through manufacturing finished articles to warehouse storage can be established inline so that productivity can be adjusted freely, each of the processes can be monitor-controlled for anchored diagnosis and thus system control, production control an inventory control can be performed.
According to the object of the present invention, there is provided an apparatus of automatically manufacturing ball studs comprising: a cold forging unit for uncoiling and forming a cold coil for ball studs into ball studs shaped at least 50% similar to a desired one; first cleaning unit for removing burrs or lubricant layers of materials from the cold forged ball studs; an impurity inspection unit for determining whether the burrs or lubricant layers are properly removed; a unit for rolling a head, a neck and threads with a rolling machine; second cleaning unit for completely removing impurities from the ball studs; an inspection unit for finding dimensional defects and minute breaks or cracks from the ball studs after the second cleaning; a storage unit for storing the ball studs into a warehouse by an automated transport robot after the inspection; a central control unit for controlling the units to be operated in sequence, performing an emergency stop of the units in response to a defect signal from the inspection unit, and diagnosing abnormal conditions of the units; and an FMS server for storing product data related to the abnormal and operated conditions and amount of production into a database and transmitting the same in the case of necessity.
Here, it is preferred that the inspection unit generates different signals according to defected parts of the head, the neck and the threads, respectively; and the central control unit receives the signals to determine which unit is malfunctioning and performs an emergency stop of the unit.
According to the object of the invention, there is also provided a method of automatically manufacturing ball studs comprising the steps of: cold forging to uncoil and form a cold coil for ball studs into ball studs shaped at least 50% similar to a desired one; first cleaning to remove burrs or lubricant layers of materials from the cold forged ball studs; impurity inspecting to determine whether the burrs or lubricant layers are properly removed; rolling a head, a neck and threads with a rolling machine; second cleaning to completely remove impurities from the ball studs; inspecting dimensional defects and minute breaks or cracks from the ball studs after the second cleaning step; storing the ball studs into a warehouse by an automated transport robot after the inspecting step; central controlling the steps to be operated in sequence, performing an emergency stop of the steps in response to a defect signal from the inspecting step, and diagnosing abnormal conditions of the steps; and storing product data related to the abnormal and operated conditions and amount of production into a database and transmitting the same in the case of necessity.
Here, it is preferred that the inspecting step generated different signals in according to defected parts of the head, the neck and the threads, respectively; and the central controlling step receives the signals to determine which unit is malfunctioning and performs an emergency stop of the unit.